First off I have XBox 360, so the following issue for F:NV (if there is such on PS3 I'm sorry I don't know how to fix it) I can help you fix if you have XBox.
I've noticed that after about an hour of play or even simply keeping your system on for over an hour in pause menu or in main menue the load times start to extend to unbelievable amounts. For me the load time started getting as long as 5 minutes long. Not to mention that even after you loaded it would freeze up a little after you loaded.
To solve this issue install F:NV to your HDD and everything will be better. Simple right?
As far as freezing up anywhere else throughout the game it still happens from time to time. I'm not sure how to fix this but my friends and I are going to see if there is a way we can do so.
So far installing it to my HDD has solved the load time issue but if it returns I'll update this with everything I have found out about it.
